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Perimetry more carefully maps and quantifies the visual field, especially at the extreme periphery of the visual field. The name comes from the method of testing the perimeter of the visual field. Automated perimeters are used widely, and applications include: diagnosing disease, job selection, visual competence assessment, school or community ...
Humphrey field analyser (HFA) is a tool for measuring the human visual field that is commonly used by optometrists, orthoptists and ophthalmologists, particularly for detecting monocular visual field. [1] The results of the analyser identify the type of vision defect.
It measures visual acuity loss: positive values indicate vision loss, while negative values denote normal or better visual acuity. This scale is commonly used clinically and in research because the lines are of equal length and so it forms a continuous scale with equally spaced intervals between points, unlike Snellen charts, which have ...
Visual acuity VA Dcc - VA Dsc Visual acuity with Distant chart with correctors Visual acuity with eye chart at Distant 20 feet (6 m) and with (cc: Latin cum correctore) correctors (spectacles); Dsc is without (sc: Latin sine correctore) correctors. See Visual_acuity#Legal_definitions: VA Nsc - VA Ncc Visual acuity with Near chart without correctors
The visual field is measured by perimetry.This may be kinetic, where spots of light are shown on the white interior of a half sphere and slowly moved inwards until the observer sees them, or static, where the light spots are flashed at varying intensities at fixed locations in the sphere until detected by the subject.
In terms of visual acuity, "foveal vision" may be defined as vision using the part of the retina in which a visual acuity of at least 20/20 (6/6 metric or 0.0 LogMAR; internationally 1.0) is attained. This corresponds to using the foveal avascular zone (FAZ) with a diameter of 0.5 mm representing 1.5° of the visual field (although often ...
Near visual acuity or near vision is a measure of how clearly a person can see nearby small objects or letters.Visual acuity in general usually refers clarity of distance vision, and is measured using eye charts like Snellen chart, LogMAR chart etc. Near vision is usually measured and recorded using a printed hand-held card containing different sized paragraphs, words, letters or symbols.
Visual hyperacuity is at least 10 times more sensitive than visual acuity, the ability to separate between distinct objects. [4] Therefore, in retinal diseases such as macular degeneration responses to hyperacuity stimuli may be abnormal long before any changes in visual acuity are observed.